This invention relates to a fluid foil bearing of the journal or radial type.
One known fluid foil bearing of this type comprises a plurality of thin resilient metal sheets or foils so arranged in the bearing housing as to surround a rotatable element or shaft to be supported by the bearing, so that as the shaft is rotated, a dynamic pressure of the fluid developed in the wedge-shaped spaces formed between the opposed surfaces of the foils and the shaft provides a bearing effect for the shaft floating in the fluid between the foils and the shaft. Since this bearing is of a non-contact type, it is substantially free from overheating, enables rotation of the shaft at a higher speed than otherwise and is suitable for use in various pneumatic machines such as turbines.
The provision of many separate foils within a narrow space between the inner circumferential surface of the bearing housing and the outer circumferential surface of the rotatable shaft, however, makes the structure of the bearing complex and bulky, and it is also difficult with the prior art arrangement to adjust the stiffnesss or spring constant of the foils.
If the foils are so arranged that they partially overlap each other, it is less likely that wedge-shaped spaces are formed between the outer circumferential surface of the shaft and the opposed surfaces of the foils, and it becomes difficult to adjust the pressure with which the foils contact the shaft, that is, the preload exerted on the shaft by the foils, so that bearings of different characteristics and capacities must be provided to provide different amounts of preload.
Accordingly, it is a general object of the invention to provide an improved fluid foil bearing which is free from the above-mentioned and other disadvantages of the prior art arrangements.
Another object of the invention is to provide an improved fluid foil bearing which is easy in adjustment of preloading of the shaft.
Another object of the invention is to provide an improved fluid foil bearing which is simple in construction, and reliable and accurate in operation.
The invention will be described in detail with reference to the accompanying drawings.